Reviewing Introduction Histories, Pathways, Invasiveness, and Impact of Non-Indigenous Species in Danish Marine Waters

Abstract

Non-indigenous species (NIS) are of concern for biodiversity conservation and ecosystem functioning. We present an updated list of NIS, including cryptogenic species, from Danish marine waters containing 123 species. Benthic invertebrates (36%) and phytoplankton (28%) dominate the list, but fish (15%) and macroalgae (13%) are also important. The Limfjord in Northern Jutland emerges as a hotspot for the introduction of NIS. Data from multiple sources were included, i.e., the National Monitoring Program (NOVANA), the National Fish Atlas project, the citizen science project Arter.dk, research articles, and annual national reports of the ICES working group ITMO. Forty-six NIS species were subject to expert judging using a modified Harmonia protocol; 19 were found to fulfil the four selected criteria identifying a species as being ‘invasive’. Additionally, 38 species, not yet recorded in Danish waters, were evaluated using the same method, and 31 were found to fulfil the ‘invasive’ criteria. For nine selected species, introduction history, distribution maps, and time-series diagrams are presented. Our data document that the national monitoring efforts should be expanded to record macrozooplankton, coastal fish, and mobile epibenthic species. Furthermore, the national data repository, Arter.dk, should be expanded to enable more detailed documentation of new NIS records.

Non-Indigenous Species Dynamics in Time and Space within the Coastal Waters of The Netherlands

“…To support strategies dealing with marine NIS, Zenetos et al [9] have presented a baseline study at European and subregional levels. To add to this European baseline study on a national level, countries such as France and Denmark have published reviews on marine NIS in their waters, evaluating and analysing their origins, pathways, and establishment [10,11]. In line with these studies, we present a review of all NIS that have been recorded over the years in the brackish to marine coastal waters of The Netherlands, including planktonic unicellular species and pathogens, such as viruses.…”

DNA metabarcoding-based detection of non-indigenous invertebrates in recreational marinas: influence of sample type and seasonal variation

“…In a recent NIS inventory in Spanish marine waters, approximately 65% of NIS were invertebrates (Png-Gonzalez et al 2023). In Danish waters, 40% of NIS were invertebrates comprising both benthic invertebrates and zooplankton (Jensen et al 2023). In a study of NIS in the coastal waters of the Netherlands, the majority of invertebrate NIS belonged to Crustacea, Mollusca, and Annelida.…”

Marine Non-Indigenous Species Dynamics in Time and Space within the Coastal Waters of the Republic of Ireland

“…In other European countries, comparable shifts in recorded higher taxa may also have occurred. However, in recent analyses, for example, Denmark [15], France [16], and Spain [17], taxonomical groups of marine NIS newly recorded up to 2020 are not separated. Therefore, it remains unclear whether particular higher taxa may have been underscored occasionally in those countries as well.…”

“…For the Celtic Seas, including Ireland and the Western English Channel waters of France, 107 NIS including parasites and pathogens are reported. Following this study on a European level, countries such as Spain, France, the Netherlands and Denmark have published reviews on marine NIS in their waters, often including unpublished records of additional NIS, and evaluating and analysing their origins, pathways, and establishment in more detail [14][15][16][17]. To complement these studies, which are focused on trends in marine NIS in Europe up to 2020, this paper presents a review and analysis of all NIS that have been recorded in brackish and marine coastal waters of the Republic of Ireland up to 2020.…”

“…For Denmark, an analysis similar to that in the present study (Figure 3) was conducted, but species were grouped by functional groups rather than by higher taxonomic categories. Although functional group analyses can provide valuable insights into NIS introductions [13,15], when interpreting results, one should be aware that possibly not all taxa representing groups like the "benthic invertebrates" were equally well monitored over time. As in the present study for Ireland where it seems likely that this was the case, and we refrain from conducting further analyses on a functional group level.…”